The Mole Concept

Counting Atoms • Chemistry is a quantitative sci scienc ence - we

need a "counting unit." • The MOLE • 1 mole is the amount of substance that

contains as many particles (atoms or molecules) as there are in 12.0 g of C-12.

 Avogadr  oPaper 

The Mole is Developed Carbon Atoms Number

Hydrogen Atoms

Mass (amu)

12

(6.02 x

Mass (amu)

1

Mass carbon / Mass hydrogen

12 amu = 1 amu

12 1 12 1

24 [2 x 12]

2 [2 x 1]

24 amu = 2 amu

120 [10 x 12]

10 [10 x 1]

120 amu = 10 amu

12 1

600 amu = 50 amu

12 1

600 [50 x 12]

Avogadro’s number 

Number

Mass Ratio

1023)

x (12)

50 [50 x 1] Avogadro’s number (6.02 x 1023) x (1)

(6.02 x 1023) x (12) = (6.02 x 1023) x (1)

12 1

Particles in a Mole

 Amadeo  Avogadro  Amedeo Avogadro (1766-1856) never knew his own number; it was named in his honor by a French scientist in 1909. its value was first estimated by Josef Loschmidt, an Austrian

(1776  – 1856)

chemistry teacher, in 1895 . ?

quadrillions

thousands trillions

billions

millions

1 mole = 602213673600000000000000 or 6.022 x 1023 There is Avogadro's Avogadro's number of particles in a mole of any substance.

Careers in Chemistry Philosopher  Q: How much is a mole? mole is a quantity used used by chemists to count atoms and  A:  A mole molecules. A mole mole of something is equal to 6.02 x 10 23 “somethings.” 

1 mole = 602 200 000 000 000 000 000 000 Q: Can you give me an example to put that number in perspective? computer that can count 10,000,000 atoms per second would   A:  A computer take 2,000,000,000 years to count 1 mole of a substance.

Counting to 1 Mole Is that right?  A computer computer counting 10 million atoms every second  would need to count for 2 billion years to count just a single mole . Lets look at the mathematics. x sec = 1 year 

365 days 24 hours 60 min 60 sec = 31,536,000 sec 1 year 1 day 1 hour  1 min

Therefore 1 year has 31,536,000 seconds or 3.1536 x 10 7 sec.  A computer counting 10,000,000 10,000,000 atoms every second could count 3.153 x 1014 atoms every year. Finally, 6.02 x 1023 atoms divided by 3.1536 x 1014 atoms every year  equals 1,908,929,477 years or approximately 2 billion years!

How Big is a Mole? One mole of marbles would cover the entire Earth (oceans included) included) for a depth of three miles. One mole of $100 bills stacked one on top of another would reach from the Sun to Pluto and back 7.5 million times.

It would take light 9500 years to travel from the bottom to the top of a stack of 1 mole of $1 bills.

 Avogadro’  Avogadro’s s Number    A MOLE

   

of any substance contains as many elementary units (atoms and molecules) as the number of atoms in 12 g of the isotope of carbon-12. This number is called AVOGADRO’s number N A = 6.02 x 1023 particles/mol The mass of one mole of a substance is called MOLAR MASS symbolized by MM Units of MM are g/mol Examples H2 hydrogen 2.02 g/mol He helium 4.0 g/mol N2 nitrogen 28.0 g/mol O2 oxygen 32.0 g/mol CO2 carbon dioxide 44.0 g/mol

1 Mole of Particles